Evaporator



June 6, 1950 BAKER ETAL 2,510,057

EVAPORATOR Filed April 24. 1944 Patented June 6, 1950 UNITED STATESPATENT OFFICE EVAPORATOR .s

Application April 24, 1944, Serial No.,532,`55`4 (Cl. S- 12) 5 Claims.

This invention relates to an evaporator for semi-liquid or plasticmaterials; Or liquids with suspended solids.

An object of the invention is to provide an evaporator of the flashYtype adapted to reduce the moisture content of such materials in aminimum of time.

Another object is to provide such a device in which, during theevaporation period, the material is simultaneously moved fromva point ofintroduction to a point of withdrawal.

Another object is to provide anvevaporator of this kind in whichthematerial is alternately spread and actuated or workedon` a dryingsurface.

Another object is the provision of a novel form of blade for such anevaporator.

Another object is to provide an evaporator of the kind described whichis simple and efficient in construction and in use.

The concentration by evaporation of` various fluid materials containingsuspended solids, such as brewers slurry, is attended by seriouspractical difficulties which are aggravated asthe materia-l approaches as emi-liquidstate of` concentration. For rapid and effective evaporationit is desirable to spread the material in a relatively thin film on aheated evaporating surface. However, if the solids in such a film areallowed to remain stationary in contact with the hot surface they willstick to and harden upon it Within a matter of seconds and anaccumulation of adfherent material will build up. The efficiency of theapparatus then progressively decreases as the evaporation process goeson, and it` isnecessary `to stop the operation and clean the evaporatingsurface at frequentintervals,` Also the adherent material tends toScorch or burn, increasing the difficulty of cleaning and deleteriouslyaffecting the finished` product into which Some of4 the scorchedmaterial finds its way. On the other hand, the adherent material removedduring cleaning` represents. a substantial loss in yield of the process.Hence it is necessary to maintain the nlm in. continuous and rapidmovement and to keep the evaporating surface scraped or wiped clean ofadherent material, while at the same time the speed of travel of thefilm through the evaporating apparatus must be slow enough to permit thedesired evaporating` effect to be obtained. ,Various forms of apparatushave beenA proposed for s uch purposes but without solving the aboveproblems satisfactorily.

According to the present invention, a blade is moved over the hotevaporating surface in a direction transverse to its length, the loweredge of the blade being interrupted at spaced points to provide a series0f Straight edges whichr advance the material in the direction ofmovement of the blade and scrape the` heating surface clear of adherentmaterial in their paths. At one end of each straight blade section, aplow-like projection extends forwardly and outwardly away from the bladesection with a forward working` face inclined transversely to thedirection of blade movement and preferably inclined also to thevertical'after the manner of aplow and its moldboard. These plowprojections substantially span the gaps between the adjacent straightsections of the interrupted blade edge and `not only scrape the materialfrom the surface in the paths of these gaps but also lift and `turn itover in front of the adjoining blade sections. The material is thuscaused to move transversely across each advancing blade` section to theother end where it passes behind the plow of the next section and hencethrough the intervening gap or opening between the sections, tending tospread out again on the evaporating surface behind the blade. Aplurality of such blades follow one anotherl in successionover theevaporating surface with their plows and intervening blade sectionsarrangedas hereinafter described so that the entire surface is scrapedand the material is kept in rapid and continuous movement and also is'overturned and agitated while it is advanced both in the direction ofmovement of the blades and transversely thereto.

By way of example an embodiment of the invention is described herein andillustrated in the accompanying drawings, in which:

Fig. 1 is a side elevational view of the evaporator.

Fig. 2 is a cross-sectional view on the line 2--2 of Fig. 1.

Fig. 3 is a plan view of one of the arms and blades of the evaporator.

Fig. 4 is a detail view of theedge portion of `one of the blades and theadjacent part of the heat,- ing chamber wall.

Fig. 5 is a schematic view illustrating the rela..- tive positions oftheedge projections on successive blades.

In greater detail, and with reference to the drawings, the evaporatorpreferably comprises a cylindrical chamber having a heated internalworking surface which may be provided by a. housing l made up of aninner cylindrical wall 2 and an outer jacket 3 spacedtherefrom andform,- ing a steam jacket or chamber 4. The housing I is suitably closedat the ends, one end being provided with an access door 5 and the otherend being formed or flared outwardly :at 6: and provided with a ue 'lfor vapors evolvedA during the evaporation process. 'I'he outer wall orjacket 3 at the top may have a steam injection manif f old 8 associatedtherewith and at the bottom a condensate outlet 9.

In the `case of a cylindrical evaporator, the blades mentioned aboveform a sort of `paddle end is an inlet I4 for the material to beoperated upon. A tangential outlet I5 for the material is provided atthe opposite end of the chamber,

preferably at the top.

Inside the heating chamber, the spreader-car- ^rier wheel or paddle isxedly mounted on the shaft It (Figs. 2 and 3). This wheel, in the formillustrated, comprises a hub I6 fixed on the shaft I 9 and provided withfour equi-distant spoke members I'I each of which carries a bifurcatedsupport I8 for a blade I9. Each support I8 comprises an upper sectionand a lower section 2| disposed at an angle thereto. At substantiallythe apex of this angle, the support I8 is .pivotally mounted at 22 onthe spoke member I'I.

VJust beyond this pivotal mounting a cross bar 23 extends between thearms of the bifurcated support I8 and limits inward pivotal movement ofthe paddle arm as a Whole relative to its associated spoke member I1, inthe manner seen in Fig. 2.

At the outer end of the supporting frame IS, an angle bracket 24 hassecured thereto at 25 a longer angle strip 25 to which the plate I9 issecured at 21. A brace strip 2S may be utilized `along the top edge ofthe blade for further se- `curing the latter in position.

The blades I9 may be formed of relatively flexible metal or othermaterial, the flexibility of which may be increased by perforating thesame as indicated at 29 at suitable intervals. The outer edge of eachblade I9 has a series of spaced projections 30 extending ahead of theblade in the direction of blade movement and also at an angle to saiddirection. These projections may be made integral with or attached tothe blade in any desired manner. They are conveniently formed by cuttingthe edge portion of the blade at an angle and bending out smalltriangular sections of the blade edge as shown in Figs. 4: and 5.

The lower edges 3! of these projections extend transversely across thedirection of blade movement and substantially span the gaps in theinterrupted lower edge of the blade I9. The forward working faces of theprojections are inclined both transversely to the direction of movementand to the vertical in the manner of a plow and its moldboard.Preferably the lower edges 3l of the projections, as'seen in Fig. 4, areformed or cut arcuately to conform to the arc or curvature of the heatedsurface 2.

Preferably and as shown in Fig. 5, all of the plows Yare arranged toturn the material over to the same side, i. e., toward the side of theoutlet 39. Also the spacing between each two adjacent projections, i.e., the length of each straight blade section, is the same along all theblade edges and is several times as great as the gaps between thesections, but the series of projections on the second blade is off-setto the right relative to the series of projections of the first bladeand so on. Thus the material streaming back through a gap of one bladespreads out in front of a straight blade section of the succeedingblade. Moreover, the amount of the off-set is such that the paralleltracks of each two successive projections such the blades and the heatedsurface.

as A and B are practically contiguous, and the same relationship existsbetween projections D and E, etc., so that when considered collectivelythe projections alone scrape over substantially the entire area of theheated evaporating surface. This is desirable because of the plowing,overturning and lateral feeding action of the plow projections asdistinguished from the straight wiping or scraping action of theintervening blade sections. In a cylindrical evaporator such asdescribed above, the successive plow projections form a continuousspiral or helix around the periphery of the paddle wheel.

In operation, power is suitably applied to the drive pulley I3 forrotating the wheel or paddle in a clockwise direction as indicated bythe arrows in Fig. 2. Centrifugal force causes the arm andblade-assemblies to swingl outwardly around their pivots 22 andmaintains the blades in contact with the evaporating surface, .thepressure of the blades against the heating surface being, however,reduced by the counterbalancing effect of the arms 20. The semi-liquidmaterial to be operated upon is introduced through the inlet I4 and isspread over the heated surface of the cylindrical chamber 2 where it iskept in continuous and rapid movement and at the same time advanced bothcircumferentially and axially by the blades. More specifically, theaction is as follows: Projection A (Fig. 5) scrapes up the material inits path and turns it over to the right in front of the adjacent sectionof the first blade. The material in this furrow being fluid, it tends toflatten and spread out further to the right, and this tendency-issupplemented positively by the advancing blade section which immediatelywipes out the furrow and causes the fluid material to spread out andflow to the right. Should the material pile up in front of the advancingblade section, it can also pass through the openings 29. Both lateraland circumferential displacement of the material take place in the aboveaction.

As the material reaches the right hand end of the blade section, itpasses behind the plow E and thus into and through the gap or openingbetween the blade sections and then spreads out again behind the rstblade. Plow B of the second blade, which is offset to the right relativeto plow A, then turns the material over to the right again in front ofthe adjacent advancing blade section with further spreading andcircumferential and lateral displacement as described above. The sameactions take place with projections C and D of the third and fourthblades,

then with projection E of the first blade, and so on. Thus the materialis carried through the chamber in a generally spiral path until it isremoved at the outlet I5. In this way the material is spread in a thinlayer on the heated surface for efficiently evaporating moisturetherefrom, but is kept in rapid and continuous movement and by virtue ofthe projections 3U is not permitted to remain spread in one position fora period of time sufficient to harden or otherwise injuriously aiTectthe material or the equipment, the material being constantly plowed upand turned over during its passage through the chamber.

Inasmuch as the arms or frame members I8 are pivotally mounted, theblades are maintained in contact with the heated surface of the chamberby centrifugal action. The construction likewise precludes unduefrictional contact between At the same time it makes possible theevaporation of the material in very thin layers about one-sixteenth (le)of an inch thick during the operating period when material is being fedinto the evaporator. When operation is stopped, the nnal rotations ofthe paddle serve to thoroughly clean the surface over which the bladespass. The speed of rotation of the paddle may be varied in accordancewith the character of the material being operated upon.

Variations will suggest themselves upon consideration of the meansherein described, but these are within the spirit and scope of theinvention and reference should be had to the appended claims for adefinition of the invention.

What is claimed is:

1. In an evaporator of the type wherein the material to be evaporated isspread in a film and moved over a heated surface, the combinationtherewith of means for spreading and moving the material comprising ablade movable over said surface in a direction transverse to its lengthand having gaps in its lower edge form ing a plurality of spaced bladeportions projections extending forwardly from the blade between saidblade portions, the working faces of said projections being inclinedtransversely to the direction of movement and the lower edges thereoftogether with the lower edges of said portions engaging the material onsaid surface, the forward working faces of the projections substantiallyspanning the gaps between adjacent blade portions so that the :combinedforward faces of said projections and portions are substantiallycontinuous from end to end of the blade While said material can movetransversely into the spaces behind the projections and through saidgaps.

2. In an evaporator of the type wherein the material to be evaporated isspread in a film and moved over a heated surface, the combinationtherewith of means for spreading and moving the material comprising ablade movable over said surface in a direction transverse to its length,longitudinally spaced sections of the lower edge of said blade beingbent forwardly from its plane on inclined bend lines to provideplow-like forward working faces that are in clined to the vertical andalso extend transversely relative to the direction of movement andacross the gaps between the blade portions to which they are joined atsaid bend lines and the adjacent portions of the blade, the lower edgesof each projection and its adjoining blade portion forming a continuousworking edge engaging the material on said surface.

3. In an evaporator of the type wherein the material to be evaporated isspread in a film and moved over a heated surface, the combinationtherewith of means for spreading and moving the material -comprising aplurality of blades movable one after another over said surface in adirection transverse to their lengths and each having gaps in its loweredge forming a plurality of spaced blade portions, a projectionextending forwardly from one end of each blade portion and transverselyacross the adjacent gap, the forward working faces of said projectionsbeing all inclined in the same direction transverse to the direction ofmovement and the lower edges of each Working face and its adjacent bladeportion being substantially continuous, whereby material scraped fromthe surface by said projections is turned over plow/like to the sameside in front of the adjacent blade portions, the projections of eachblade being off-set toward said same side relative to the projections ofthe preceding blade and the combined working edges of said projectionsscraping substantially the entire heated surface.

4. In an evaporator of the type wherein the material to be evaporated isspread in a film and moved over a heated substantially cylindricalsurface, the combination therewith of means for spreading and moving thematerial comprising a blade extending in a direction parallel to thecylinder axis and movable circumferentially over the surface with itslower edge parallel thereto and engaging said material thereon, saidlower edge having longitudinally spaced gaps therein, and projectionsextending forwardly from the blade at an angle transverse to itsdirection of movement, one such projection extending forwardly from oneside of each gap in the interrupted blade edge and substantiallyspanning the gap, the lower edges of said projections being curved toconform to said surface and engaging and scraping said surface wherebymaterial thereon is turned over in front of the advancing sections ofthe lower blade edge.

5. In an evaporator of the type wherein the material to be evaporated isspread in a lm and moved over the heated surface of a cylindricalchamber in a direction parallel. to the axis thereof, the combinationtherewith of a carrier mounted coaxially within the chamber forrotation, longitudinally extending blades for the carrier and eachhaving a working edge cooperating with said surface and formed by anumber of longitudinally spaced, spreader portions having edges parallelto said surface and plow-shaped members formed between adjacent portionsand projecting ahead of the blade at an angle transverse to thedirection of rotation, the working edges of said member being curved toconform to the cylindrical surface of the working chamber, said membersbeing each adapted to turn over and mix the material and also advancingsaid mixed material into the path of an adjacent spreader portion, themembers of each blade being offset in the same longitudinal directionwith respect to the members of the preceding blade and the combinedworking edges of said members traversing substantially the entirecylindrical surface of the chamber as said carrier rotates.

STANLEY L. BAKER. CHARLES J. BUTZINE.

REFERENCES CITED The following references are of record in the

